Is it ok to Bi-amp using different Brand/model of

My concern is different input sensitivity of the amps. The VK-60 is 1.0V. The SS BAT amps are rated at 1.5V. Does this mean when adjusting the volume on the pre-amp the gain on the two amps change at different rates. That is, do I need to re-adjust the level controls on the Active XO to balance the gain on the woofer and mid-tweeter sections with each diffent pre-amp volume settting.

No, once levels are matched between the woofers and mid/hi drivers, they will stay matched as you change the volume control setting.

BTW, what you are matching is amplifier gains, not sensitivities. The sensitivity of each amp is the input voltage it requires to reach its particular maximum rated output power. For instance, if all of the speaker's internal crossover elements were in place, and you were to drive the woofers with a 200W amp having 1.0 volt sensitivity, and you were to drive the mid/hi's with a 100W amp also having 1.0 volt sensitivity, the input to the 200W amp would have to be attenuated by 3db for a proper match.

The fact that you have the speakers' mid/hi crossover elements in place, with the woofers' crossover elements removed, complicates things a bit further, because the crossover will introduce some loss at mid/hi frequencies but not at low frequencies. But once you obtain a satisfactory volume match, it will not have to be readjusted as you change the volume control.

I'm wondering, though, about crossover slopes. I note in Figure 3 of Stereophile's measurements that the crossover slopes of the mid/hi section appear to be asymmetrical with respect to those of the woofer section (approximately 24db/octave for the woofer section, and close to 12db/octave for the mid/hi's), although that figure presumably represents the combined rolloffs of both the crossover network and the drivers. If you are saying that in your setup only the active xo is rolling off the woofers, while both the active xo and the internal xo of the speaker are in the path to the mid/hi drivers (with all of the crossover points being about 550Hz), it seems to me that (depending on what the active xo slopes are) you may be making the overall crossover characteristic significantly different than what was provided in the original design.

Regards,
-- Al

Thanks Stanwal. That was the answer I was looking for.
Regards,
Norm

Hi Al,

Very astute of you to notice the slopes are indeed not symmetrical on the Hales as noted on the Stereophile’s measurements. I did experiment with different slopes (i.e. 12 db slopes and did not like how it sounded) but ended up using LR 24 db slope on both the woofer and mid-tweeter section. However, I never tried to duplicate the off-setting slopes of the original design. I will give that a try.

Would you please elaborate further on your 3rd paragraph (“complicates things a bit further, because the crossover will introduce some loss at mid/hi frequencies but not at low frequencies”), didn’t get what you mean. Thanks.

Regards,

Norm

when you changed crossover slope, you also changed the phase relationship between drivers.

Would you please elaborate further on your 3rd paragraph (“complicates things a bit further, because the crossover will introduce some loss at mid/hi frequencies but not at low frequencies”), didn’t get what you mean. Thanks.

Hi Norm,

I'm envisioning that resistors which may be present in the speaker's crossover, and/or to a much lesser degree the dc resistances of its inductors, may be significant contributors to the relative balance of lows and mid/hi's.

Since you have bypassed the low frequency section of the speaker's crossover, but not the mid/hi section, you may therefore be raising the sensitivity of the speaker to low frequencies relative to its sensitivity to mid/hi frequencies. If so, the level matching you would have to accomplish with the active crossover would have to reflect that difference, in addition to the difference in amplifier gains.

Regards,
-- Al